In the News (Wed 19 Dec 18)

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus).

The gas planets do not have solid surfaces, their gaseous material simply gets denser with depth (the radii and diameters quoted for the planets are for levels corresponding to a pressure of 1 atmosphere).

Jupiter is about 90% hydrogen and 10% helium (by numbers of atoms, 75/25% by mass) with traces of methane, water, ammonia and "rock".

Jupiter possesses 28 known satellites, four of which - Callisto, Europa, Ganymede and Io - were observed by Galileo as long ago as 1610.

This true color mosaic of Jupiter was constructed from images taken by the Cassini spacecraft on December 29, 2000, during its closest approach to the giant planet at a distance of approximately 10 million kilometers (6.2 million miles).

Jupiter's diameter is eleven times that of Earth, so the smallest storms on this mosaic are comparable in size to the largest hurricanes on Earth.

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus).

The gasplanets do not have solid surfaces, their gaseous material simply gets denser with depth (the radii and diameters quoted for the planets are for levels corresponding to a pressure of 1 atmosphere).

The mean density of Jupiter is therefore only about one quarter that of the Earth, indicating that the giant planet must consist of gas rather than the metals and rocks of which the Earth and the other inner planets are composed.

Jupiter may therefore represent a direct condensation of a portion of the primordial solar nebula—the great cloud of interstellar gas and dust from which the entire solar system formed about 4.6 billion years ago.

However, Jupiter would need to be almost 100 times as massive to produce a temperature at its centre high enough to release nuclear energy in reactions like those that power the Sun and other stars.

The sensitive instruments aboard found that the Jovian magnetic field's "north" magnetic pole is at the planet¹s geographic south pole, with the axis of the magnetic field tilted 11 degrees from the Jovian rotation axis and offset from the center of Jupiter in a manner similar to the axis of the Earth's field.

Jupiter may therefore represent a direct condensation of a portion of the primordial solar nebula, the great cloud of interstellar gas and dust from which the entire solar system formed about 4.6 billion years ago.

Closer to the planet, the Voyager spacecraft discovered a faint system of rings with material that must be continuously renewed and is probably produced by the disintegration of small moonlets imbedded within the rings.

Despite striking the far side of the planet, as seen from Earth, the impacts caused explosion after explosion - and it was to be recorded by every telescope on Earth, the H.S.T. in orbit, and the Galileo probe, still 18 months away from Jupiter.

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus).

The gasplanets do not have solid surfaces, their gaseous material simply gets denser with depth (the radii and diameters quoted for the planets are for levels corresponding to a pressure of 1 atmosphere).

However, Jupiter still appears fairly bright due to its size, and is the 4th brightest object in the night sky.

The stripes which are visible on Jupiter's surface are caused by streams of fast, powerful winds which blow at over 400mph alternately in opposite directions across the planet (in the east-west directions).

Radiation is slowly emitted in the infra-red, and theoretically causes the planet to gradually decrease in volume by a tiny amount.

Jupiter, together with its four largestmoons, which range from the size of the Earth'smoon to the size of the planetMercury, are in some ways analogous to a mini-solar system, Jupiter being analogous to the sun as the central body, and Jupiter'smoons being analogous to the planets.

Jupiter's magnetic field is the strongest in the solar system, except for fields associated with sunspots and other small regions on the sun's surface.

On the side of the planet away from the sun, the magnetosphere stretches out into an enormous magnetic tail, often called a magnetotail, that is at least 435 million miles (700 million kilometers) long.